In the handling of cargo, the use of automatic container identifying means is increasing. In a typical system, each container is provided with a coded marking or label on the surface, which marking may be identified or "read" by an optical or microwave scanner.
The coded label on the container may provide, through the scanner, data to a computer to record the receipt or shipment of the cargo, its storage location, its destination, ownership, and other data.
To be most effective, the containers should be "scanned" to identify the contents from the coded markings as they are loaded or unloaded from the transport means, which requires that the cargo handling means must carry the containers past the scanner. When containers are being loaded or unloaded from a truck or railroad car or when being taken to or from a storage warehouse, it may be convenient to insure that the containers pass by a scanner. However, in attempting to scan the containers when cargo is being for example unloaded from a ship, with the containers being lifted off the deck or out of the hold and transferred horizontally and lowered onto a truck, railroad car, or merely to a storage position, (or when being loaded with the reverse procedure occurring) it has been found difficult to insure that the container passes the scanner at the proper elevation to allow the scanner to read the coding on the container. Although it would be theoretically possible to lift the container from the ship to a predetermined level, transfer it horizontally past a scanner at the predetermined level, and then lower it onto a truck, conveyor, or to a storage position, in actual practice the crane operator starts the lateral movement of the crane mechanism as soon as the container is clear of the vessel, while still continuing a vertical motion to reduce to a minimum the time taken to transfer the container. Hence it is impossible to predict the exact height above ground that the container will be when it passes the scanner position. pg,3